This commit adds support for input ABI 12, consisting of a number of
changes:
- requires an X server with an ABI of 12
- valuators have a per-mode setting
- new PreInit prototype.

Because of the new PreInit prototype, the hotplug system has been switched
around too (should have probably been done in a separate commit before,
but...).

The old hotplug mechanism added a separate ModuleInfoRec for the keyboard
part of the driver. This isn't feasable for InputClass configurations, the
driver part may get overwritten.

On entering the driver, after checking a few default values, hotplug the
keyboard device (wacom-style) and let it initialize. Because NIDR calls
DEVICE_INIT and DEVICE_ON the keyboard must initialise the private pointer
and pass it back to the original device.

Call order is:
NewInputDeviceRequest
 - jstkCorePreInit
   - jstkKeyboardHotplug
     - NewInputDeviceRequest
       - jstkCorePreInit
         immediately return jstkKeyboardPreInit()
       - keyboard DEVICE_INIT
       - keyboard DEVICE_ON
     return keyboard device
   - copy keyboard->priv to joystick->priv
   - finish jstkCorePreInit as normal
   - joystick DEVICE_INIT
   - joystick DEVICE_ON

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Trevor Woerner <twoerner@gmail.com>